Nutrient burn, sometimes called nitrogen burn, is a sign of stress when plants are given excessive nutrients. In the same way that plants need water but can die when overwatered, nutrient burn occurs when you overfeed a plant, saturating it with too much fertilizer.
Nutrient burn could happen to many homegrown plants, such as tomatoes and other fruits and veggies, but it is often associated with cannabis. Nutrients are important for growth and good yields of fruit, or in the case of cannabis, the buds. However, more is not always better, and too much fertilizer could cause damage, which in turn stifles growth and bud or fruit production.
An inexperienced grower may be very excited and focused on high yields, leading them to fertilize as much as possible. Yet there is a limit to how much you can “feed” plants, and unlike animals, plants have no way to store excess nutrient energy, such as inside fat cells.
How To Spot Nutrient Burn
Severe nutrient burn can damage roots, but the most obvious sign of damage is when the leaves start to turn brown and scorched at the tips and edges as if slowly burning. The damaged parts of the leaves cannot absorb light for photosynthesis, further exacerbating the plant’s health issues. If this scorching appears even when you’re watering the plant well â€” and the leaves don’t appear wrinkled or dry as if dehydrated â€” you may have overfertilized them.
The early warning signs of nutrient burn are overly dark green leaves, slight yellowing or browning at the leaf tips, and bending at the leaf tips. If the plant remains in oversaturated conditions, the leaf tips will bend further back and inward, and the scorching, yellowed color will travel further down the leaf. This progression will continue until affected leaves start to die and fall off.
How to Fix Nutrient Burn
Will plants recover from nutrient burn? Absolutely, if you catch and address the problem early enough. As soon as you notice the issue, you need to figure out which nutrient is overabundant and balance it back down to a healthy amount. Most nutrient burn problems come from excessive nitrogen, but some growers will mistakenly increase other nutrients that may have more subtle signs.
The leaves that were damaged by nutrient burn will not recover and turn fully green again, so do not use those leaves as a sign that you have fixed the problem. Instead, look to other healthy leaves nearby and take pictures every day to ensure they aren’t “burning.”
To put a stop to nutrient burn, follow these steps:
- Flush out the excess nutrients.Â If you are using a hydroponic setting, such as coir for cannabis, nutrient burn may be affecting all plants sharing that reservoir. Flush the roots with fresh pH-balanced water. In a hydroponic setup, that means draining the reservoirs and refilling them with fresh water. In a soil mixture, ideally in a perforated pot, you can run a hose onto the base of the stem and let water filter through the bottom.
- Test for nutrients via EC levels. In both cases, use a TDS meter to test the nutrients. With hydroponics, simply test the electrical conductivity (EC) level in the reservoir liquid until it is close to zero. With soil, test the runoff from the pots or ground until it is slightly lower than the recommended nutrient levels.
- Add nutrients again, carefully. Remember, the plants themselves are still overloaded. Wait until the burning has stopped, and then start with about half of what you would normally use according to instructions. After that, monitor the progress. You can always add slightly more nutrients later and check the leaves over the following days.
For potted plants or those in the ground, you may need to take more careful measures with the fertilizer you prepared. Some ingredients, such as fresh manure, may need to be used in smaller quantities in ratio with plain soil or other less nutritious materials.
What if You Have Severe Nutrient Burn?
Nutrient burn will impact yield potential on plants because they have to invest a lot more of their energy into staying alive than they normally would. If you have a severe case of nutrient burn, the natural conclusion is that you simply used an especially high amount of fertilizer products. However, the situation may be more nuanced than that, and you need to address other contributing factors. For example:
- If your plants are not receiving enough light throughout the day, that could be exacerbating the problem. Plants use sunlight to process nitrogen and other essential fertilizer ingredients. If the plant doesn’t get as much light as it needs for optimal growth, it has a reduced capacity per day to process nutrients, similar to a starved animal having a smaller stomach. Overfeeding in such a case would only cause more harm.
- Different crops, or different plants in a crop, may have different nutrient needs. If you grow multiple plants, make sure to monitor them and make adjustments to their nutrient supply. In a hydroponic setting, it will be important to find a balance that allows all plants in the same reservoir to have the right amount of fertilizer.
- Sometimes, growers mistakenly add too much of a nutrient that a plant doesn’t need much of in the first place. For instance, when growing cannabis with coir, it helps to use a calcium-magnesium solution. However, if you overfeed with these elements along with nitrogen and others, the nutrient burn progression will be that much more extreme than nitrogen-only nutrient burn.
Nutrient burn is an avoidable mistake, and it’s relatively easy to correct when caught early. Check for the signs with every new plant or crop you grow, and if you catch it quickly, a simple wash, followed by reintroducing a lower concentration of fertilizer, should help your plants get back to perfect health.